Window for a laser tube end piece

ABSTRACT

A window for a laser tube end piece, made of doped semiconductor material comprising super-doping in the vicinity of the parts of the windows which are to come in contact with the end pieces of the laser tubes.

XFZ 397159684 States atent 91 Feb. 6, 1973 WINDOW FOR A LASER TUBE ENDPIECE lnventor: Jean-Pierre Biet, Saulx-les-Chartreux, France Assignee:Compagnie General DElectricite,

Paris, France Filed: April 10, 1972 Appl. No.1 242,537

Foreign Application Priority Data April 9, 1971 France ..7l l2779 us. 01..33i/94.s, 350/319 rm. Cl ..H01s 3/08 Field of Search ..33l/94.5;350/319 [56] References Cited OTHER PUBLICATIONS Large et al., A compactPulsed Gas Laser for the Far Infrared; Applied Optics, Vol. 4, No. 5(May 1965) pp. 625 and 626.

Primary Examiner-William L. Sikes Attorney-Richard C. Sughrue et al.

[57] ABSTRACT A window for a laser tube end piece, made of dopedsemi-conductor material comprising super-doping in the vicinity of theparts of the windows which are to come in contact with the end pieces ofthe laser tubes.

11 Claims, 1 Drawing Figure WINDOW FOR A LASER TUBE END PIECE BACKGROUNDOF THE INVENTION l. Field of the Invention The present inventionconcerns plates for laser tubes, and more particularly plates for lasergenerators which emit an infrared radiation, such as CO lasergenerators.

2. Description of the Prior Art A discharge tube of a laser generator isgenerally closed at least at one of its ends by a transparent opticalblade such as, for example, a blade placed at Brewster incidence.

The service life of certain blades closing up laser tubes is limited bythe effect of the thermal stresses which they have to undergo such as inthe case of the CO molecular lasers which send out energy capable ofreaching several kilowatts. These blades eventually break as soon asthere is a sufficient rise in temperature.

The rises in temperature in a Brewster incidence plate are caused by thefact that the material with which the blade is made is not completelytransparent to the laser radiation, typically having a wavelength of10.6 microns, and the light energy absorbed by the latter is transformedinto thermal energy which is not negligible due to the high density ofpower of the beam.

In tubes manufactured heretofore the least variation in temperature hascreated a stress in the blade which caused the damaging of the latter bemelting, dissociation, mechanical breakage or overheating, thus makingit necessary to replace the blades and therefore also-to make a newadjustment of the laser parameters.

To overcome these disadvantages a proposed solution has been to arrangeon the end fittings forming the support of the laser tube output plate,radiators enabling the faster dissipation of calorific energy producedby the absorbing of the laser radiation by the material with which theoutput plate was made.

Deposit this action, it has been observed that the blades have too shorta service life to enable laser generators which are to be fitted withsuch blades to be properly industrialized.

OBJECTS OF THE INVENTION An object of the present invention is to avoidsuch operating incidents as described heretofore by improving thedissipation by conductivity of the heat produced in the blade byabsorption of a part of the radiation of the laser generator, whilesimultaneously preserving a good light transmission of the latter.

Another object of the present invention is a plate for a laser tube endfitting consisting of a blade made of semi-conductive transparentmaterial comprising a particular doping, characterized in that the bladecomprises on at least a part of its periphery which is to be crossed bythe beam coming from the laser tube, an excess doping of the same typeso as to obtain, in said peripheral part, a semi-conductive materialdegenerated at its surface.

Other objects of the invention will be obvious to those skilled in theart as the description of the invention proceeds.

BRIEF DESCRIPTION OF THE DRAWING The present invention will be betterunderstood from the following description given with reference to theaccompanying drawing, by way of illustration but which is not intendedto be limiting, in which the FIGURE shows a sectional view of anembodiment of a plate placed on the end ofa laser tube end fitting.

DETAILED DESCRIPTION OF THE INVENTION The FIGURE shows an optical plateconsisting of a blade I placed for example at Brewster incidence on theend of a laser discharge tube 2, partly illustrated. The laser beam 3coming from the tube 2 crosses the blade 1 in its central part 4. Whenthe laser generator comprising the tube 2 is a generator emitting aninfrared beam, such as, for example, CO laser generators emitting on awavelength of 10.6 microns, the blade 1 is made of a transparentmaterial which is generally a semi-conductive material such as, forexample, one of the following bodies: germanium, gallium arsenide,silicon, etc. The blade 1 is made so that the central part has a dopingof a determined type, that is, either of the N type (for examplegermanium doped with phosphorus or with antimony) or of the P type(germanium doped with boron or with aluminum, or with gallium or withindium).

To improve the thermal conductivity and the dissipation of heat by theabsorbing of the beam 3 in the central part 4 of the blade 1, I haveproduced, in the peripheral part 5 of the blade 1 (and preferably in theI part in contact with the end fitting of the discharge tube 2) anexcess doping of the semi-conductive material of the same type as thedoping, so as to obtain, in the peripheral part 5 of that plate 1, asemi-conductive body degenerated at its surface; for example, if thesemi-conductive body is a doped body of the N type, the excess dopingwill be of the N type, whereas if the semi-conductor is a body of the Ptype, the excess doping will be of the P type.

It must be understood that the excess doping process on the peripheralpart of the plate can be chosen from among known processes such asalloying, diffusion and epitaxy. I

To improve the contact between the window 1 and the end of the laserdischarge tube 2, which is generally metallic, the plate'comprises onthe peripheral part of the blade intended to be placed in contact withthis tube 2, a thin intermediate metal layer 6 deposited, for example,by evaporation in a vacuum, cathodic spray"- ing, serigraphy, etc. Thatmetal layer 6 can be, for example, a layer of aluminum, of copper, ofgold or any other material which is a good heat conductor. The contactbetween that metal layer 6 and the end fitting of the tube 2 is theneffected, for example, by pressure or by soldering.

It is claimed:

1. A plate for a laser end fitting for a laser beam apparatus comprisinga blade made of a semi-conductive material, comprising a doping of acertain type, characterized in that said blade comprises, on at least aperipheral part of the portion of said blade intended to be crossed by abeam coming from said laser beam apparatus, an excess doping of the sametype so as to obtain, in said peripheral part, a semi-conductivematerial degenerated at its surface.

2. The plate according to claim 1, characterized in that it comprises athin metal layer arranged on at least a part of the surface of theperipheral part of said blade containing said excess doping.

3. In a laser beam apparatus comprising a plate for a laser end fitting,said fitting comprising a blade made of a semiconductive material, theimprovement comprising said blade containing a doping on at least theperipheral part of the portion of said blade which is crossed by a beamfrom said laser beam apparatus whereby said semi-conductive material isdegenerated at its surface.

4. The apparatus according to claim 3 wherein said semi-conductivematerial is selected from the group consisting of germanium, galliumarsenide and silicon.

5. The apparatus according to claim 3 wherein the central portion ofsaid blade contains an N type doping.

6. The apparatus according to claim 5 wherein said doping is selectedfrom the group consisting of phosphorus and antimony.

7. The apparatus according to claim 3 wherein the central portion ofsaid blade contains a P type doping.

8. The apparatus according to claim 7 wherein said P type doping isselected from the group consisting of boron, aluminum, gallium andindium.

9. The apparatus according to claim 3 wherein said peripheral part ofsaid blade contains a thin metallic layer selected from the groupconsisting of aluminum, copper and gold.

10. The apparatus according to claim 3 wherein said peripheral part ofsaid blade contains a heat-conducting thin metallic layer.

11. A plate for a laser tube end fitting comprising a blade made of asemi-conductive transparent material containing a doping on said blade,the periphery of said blade containing an excessive doping whereby saidsemi-conductive material is degenerated at its surface containing theexcessive doping, said periphery being exposed to a laser beam which isemitted from a laser tube.

1. A plate for a laser end fitting for a laser beam apparatus comprisinga blade made of a semi-conductive material, comprising a doping of acertain type, characterized in that said blade comprises, on at least aperipheral part of the portion of said blade intended to be crossed by abeam coming from said laser beam apparatus, an excess doping of the sametype so as to obtain, in said peripheral part, a semi-conductivematerial degenerated at its surface.
 2. The plate according to claim 1,characterized in that it comprises a thin metal layer arranged on atleast a part of the surface of the peripheral part of said bladecontaining said excess doping.
 3. In a laser beam apparatus comprising aplate for a laser end fitting, said fitting comprising a blade made of asemi-conductive material, the improvement comprising said bladecontaining a doping on at least the peripheral part of the portion ofsaid blade which is crossed by a beam from said laser beam apparatuswhereby said semi-conductive material is degenerated at its surface. 4.The apparatus according to claim 3 wherein said semi-conductive materialis selected from the group consisting of germanium, gallium arsenide andsilicon.
 5. The apparatus according to claim 3 wherein the centralportion of said blade contains an N type doping.
 6. The apparatusaccording to claim 5 wherein said doping is selected from the groupconsisting of phosphorus and antimony.
 7. The apparatus according toclaim 3 Wherein the central portion of said blade contains a P typedoping.
 8. The apparatus according to claim 7 wherein said P type dopingis selected from the group consisting of boron, aluminum, gallium andindium.
 9. The apparatus according to claim 3 wherein said peripheralpart of said blade contains a thin metallic layer selected from thegroup consisting of aluminum, copper and gold.
 10. The apparatusaccording to claim 3 wherein said peripheral part of said blade containsa heat-conducting thin metallic layer.